border-1px($color)
  position: relative
  &:after
    content: ''
    position: absolute
    bottom: 0
    left: 0
    display: block
    width: 100%
    border-top: 1px solid $color
border-none()
  &:after
    display :none
bg-img($url)
	background-image: url($url + "@2x.png")
	@media(-webikit-min-device-pixel-ratio:3),(min-device-pixel-ratio:3)
		background-image: url($url + "@3x.png")
